Process of making ammonium nitrate by the ammonia-soda process.



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ma n sraruspapunr orriou v FRANCIS A. FREETH, 9F GREAT EROSBY, AND HERBERT E. GGGKSEBGE. 9] LONDON.

. ENGLAND.

PROCESS OF MAKING AMMONIUM NITRATE BY THE AMMONIA-SODA PROCESS.

No Drawing.

To all whom it may concern Be it known that we, FRANCIS ARTHUR l nnu'rn and Hammer ED IN Cocnsnucu, subjects of the King of Great Britain, residing, respectively, at Great Crosby, in the county of Lancaster, and Herne Hill, E, London, both in the Kingdom of England, have invented certain new and useful Tm provements in Processes of Making Ammonium Nitrate by the Ammonia- Soda Process, of which the following is a specification.

There has hitherto been no industrially practicable method for the manufacture of pure ammonium nitrate from sodium nitrate by means of what is known as the ammania-soda reaction, because the reaction as hitherto performed is too incomplete to render possible the direct separation of ammonium nitrate from the solutions in a suiticiently pure state.

We have discovered a process whereby, in the reaction of ammonium bicarbonate or of ammonia and carbon .dioxid with sodium nitrate in presence of water, the proportion of sodium nitrate transformed into ainmonium nitrate is so greatly increased, and the proportion oil ammonium nitrate to water in the solution resulting from the reaction after separation of the sodium bicarbonate precipitated by the reaction is such, that a considerable yield of pure or practically pure ammonium nitrate in the solid form can be obtained directly by cooling the solution after a preliminary treatment for the destruction of the bicarbonates contained in it.

Our process depends upon the hitherto unrecognized fact that, in the reaction between ammonium bicarbonate (or its components, carbon diorrid and ammonia) and sodium nitrate in presence of water, the maximum possible formation of ammonium nitrate at any given temperature at which the reaction is performed is attained when the proportion ot these reacting substances and of Water are so adjusted that (a) no sodium nitrate remains undissolved when the reaction is finished. (Z2) The solution resulting from the reaction, after removing the bicarbonate of soda precipitated, is saturated at the temperature at which the reaction was performed (that is, at the temper-attire at which the bicarbonate of soda was removed) with respect to ammonium ftpecifieation of Letters Patent.

Application filed June 5, 1511.

Patented Dec. 9, 1913.

Serial No. (331,401.

bicarbonate, sodium bicarbonate and ammonium nitrate. lt is to be understood that in the above and on all subsequent occasions when the expressions temperature of reaction or temperature at which the reaction was performed are used, those expressions mean the temperature which obtained during the operation of removing the bicarbonate cl soda precipitated by the reaction ifrom the solution 01" salts resulting from the reaction. The mixture of the reacting salts and water need not necessarily be maintained at that temperature during the whole of the period preceding the removal of the precipitated bicarbonate of soda. The temperature at which the reaction is performed must not of course be above that at which the tormation of a reasonable quantity of ammonium nitrate is possible; the upper practicable limit of temperature is about 35 to to 0, but it is preferable to work at a temperature below 35 (3; We have tound that in order to obtain these results it is necessary to employ for the reaction a minture of sodium nitrate, ammonium bicarbonate or its components, and Water, containing a considerably larger quantity of sodium nitrate than will dissolve in. the water at the temperature of reaction. For example, a solution saturated with ,respect tov ammonium bicarbonate, sodium leicarbonateand ammonium nitrate at 25 (3., and containing 186 parts ot ammonium nitrate, 3.2 parts of ammonia other than that combined as ammonium nitrate, 8.4 parts of carbon dioxid, 36 parts olsodium nitrate and 100 parts of water, results from the reaction between 5233.6 parts of sodium nitrate and 198.6 parts of ammonium bicarbonate in presence of 100 parts oil water at 25 C", after the precipitated bicarbonate oi" soda has been removed at 25 C. This opian tity oi sodium nitrate is considerably greater than will dissolve in the Water at 25 C.

We find that a solution resulting from the reaction between sodium nitrate and ammonium bicarbonate (or its components) which is saturated with respect to ammonium bicarbonate, sodium bicarbonate and ammonium nitrate at the temperature at which the reaction was performed can be cooled to a very low temperature, even to minus 25 0., without separating out the sodium nitrate which it contains. We find further that if this solution be first treated in such a way as to remove the whole or the greater part of the bicarbonates which it contains and be then subsequently cooled to a temperature below that at which the reaction was performed, crystals of ammonium nitrate are separated out which, after suitable washing to remove adherent mother liquor, are pure or practically pure.

The removal of the bicarbonates may be efiected by heating the liquor either at or below atmospheric pressure for a suiiicient time: if at atmospheric pressure we find that a temperature of 60.to C. is suit able, whereas-a temperature of 10 to 50 C. is suitable at a vacuum of 26 inches of mercury, but we do not confine ourselves to these temperatures or pressures. The removal of the bicarbonates may also be effected by neutralizing the solution with nitric acid or by other suitable means.

The yield of solid ammonium nitrate obtained on cooling varies with the extent to which the cooling? is carried.

If to the mother liquor after separation of the ammonium nitrate, equivalent quantities of ammonium bicarbonate (or its com ponents) and sodium nitrates are added in such quantities that the amount of sodium nitrate. added is equivalent to the ammonium nitrate removed by cooling (except that these quantities must be adjusted to compensate for the small amounts of ammonia, carbonic acid and water, or any of them, lost during the process of removing the bicarbonates in solution, or lost in other ways as well as for additions due to wash water) then the resultant'mixture if treated in precisely the same way as before, the reaction and the cooling being both performed at the same temperatures respectively as in the previous operation, will yield precisely the same results, and the liquors resulting from the several processes will have the same composition as in the previous cycle of operations. This cycle of operations can be repeated and continued indefinitely.

It is obvious that if for any reason it is wished to vary either the temperature at which the reaction is erformed or the temperature to which t e liquors are subsegliliently cooled, or both, the composition of e reacting-solution can easily be adjusted to the changed conditions, at the beginning of the next cycle.

If the cooling for separation of ammonium nitrate be carried only to that extent which sufices to separate a quantity of ammonium nitrate not greater than is equivalent to that quantity of sodium nitrate which will dissolve in the mother liquor from which the ammonium nitrate has been separated when its temperature is raised to a pointnot higher than'that at which the re between ammonium bicarbonate and ate or soda resulting may be prepared and employed in the original operation with which the process started, whereby the presence of undissolved sodium nitrate is avoided even in the initial .operation, the reacting solution being then prepared by adding to the artificial mother liquor equivalent quantities of sodium nijtrate and ammonium bicarbonate (or its components), the sodium nitrate being added in that quantity which will entirely dissolve in the liquor.

In actual practice we may so work our process that the liquor resulting from the reaction is not completely saturated with respect to ammonium bicarbonate and ammonium nitrate at the temperature of the reaction, and thereby leave a margin of safety sufficient to avoid the danger of pro cipitating these salts together with the bicarbonate of soda.

Our process therefore consists in causing to react together such quantities of sodium nitrate, ammoniumbicarbonate (or its components) and water at any temperature at which these substances will form ammonium nitrate, as will yield when the reaction is finished and after the recipitated bicarbonfrom the reaction has been removed at the temperature of the re action, a solution saturated with respect to sodium bicarbonate and also saturated or nearly saturated with respect to ammonium bicarbonate and ammonium nitrate at the temperature of the reaction. The bicarbonate of soda is removed from the solution at the temperature of the reaction, by filtration or other well known means, is washed to remove adherent mother liquor, and is then pure or practically pure. The solution from which the bicarbonate of soda has been removed is then treated for the removal of the whole or the greater part of the bicarbonate in solution as previously d scribed, and is subsequentl cooled to a temperature below that at which the reaction was performed, and which may be as low as minus 25 C. if desired when crystals of'ammonium nitrate separate outwhich are removed from the solution and washed preferably with a saturated or partially saturated solution of ammonium nitrate, and dried by any well known means. They are then pure or practically pure. To the mother liquor remaintill neutron ing after'removal ot the ammonium nitrate are added, either before, during or after heating to the temperature at which the re action is to be performed, equivalent quantities of ammonium bicarbonate (or its components) and sodium nitrate in such quantity' that the latter is equivalent in amount,

to the ammonium nitrate which has been removed by cooling, except that small adjustments must be made to compensate for losses during the process of removing the soluble bicarbonates, for addition of wash water,"&c., the amount of which can easily be determined by simple tests. The cycle of operations is then repeated and may be continued indefinitely or until the liquors have become so impure as to require replacement.

Example: 200 parts by weight of sodium nitrate, 210 parts or ammonium bicarbonate, and 100 parts of water are stirred together at any temperature between 33 and 22 centigrade, and when the reaction is tinished the precipitated bicarbonate of soda is separated from the solution at 22 centigrade. The remaining solution then contains about all) parts of sodium nitrate, 161 parts of ammonium nitrate, and 100 parts of water, together with some ammonia other than that contained in the ammonium nitrate, and carbonic acid: when this solution is first treated as previously described in such a way as to remove the whole or the greater part of the'bicarbonate which it contains, and is thensubsequently cooled, it yields solid ammonium'nitrate as follows, per 100 parts of water :by cooling to 1 centigrade, about 55 parts of ammonium nitrate; by cooling to --8 centigrade, about parts or ammonium-nitrate; by cooling to -.-13 centigrade,-about 85 parts of ammonium nitrate; by cooling to 22 centigrade, about 100 parts of ammonium nitrate.

We may, instead of employing in the initial cycle of our process the mixture of sodium nitrate, ammonium bicarbonate and water described above, use as the medium to which the sodium nitrate anti ammonium bicarbonate are added, an artificial mother liquor made by dissolving ammonium nitratevand sodium nitrate in water in such proportions as will enable the resulting so-' lution to dissolve entirely the required quan tity of sodium nitrate, and so avoidthe' inconvenience of having sodium nitrate in susension during the reaction which results in the precipitation oil sodium bicarbonate.

it in our process it is desired to separate the greater part of the ammonium nitrate from the mother liquor remaining after cooling, either because the liquid has become too impure or for other reasons, we may proceed as tollows:The mother liquor is concentrated until it is nearly saturated with ammonium nitrate at 50 to 60 U: it can then quently any excess of sodium nitrate above this ratio is precipitated; The precipitate is separated from the solution at 50 to 60 C. and the latter is then cooled with the addition of suiiicient water to keep the sodium nitrate in solution at the temperature to which it is to be cooled. Un cooling, ammonium nitrate separates out which, after separation li-om the solution, and suitable washingto remove adherent mother liquor, is pure or practically pure. The liquor from which the ammonium nitrate is separated may again be concentrated andprecisely the same seriesot operations repeated, and so on as often as desired. For example, if the liquor concentrated as, described, is to be cooled to minus 22 C. it must contain about 190 arts by weight of water for each 100 parts y weight of sodium nitrate, and previous to cooling, water must be added until that proportion obtains: at minus 22 C. it can only hold in solution about one part by weight of ammonium nitrate for eachone part of sodium nitrate which it contains: consequently the excess of ammonium nitrate above that ratio is precipitated, i

We declare that what we claim is 1. The process for the manufacture of commercially pure ammonium nitrate, which consists in causing to react with for? mation 0t ammonium nitrate, such quantities of sodium nitrate and a suitable reagent or reagents in presence of such quantity of water as will yield when the reaction is .finished a precipitate of sodium bicarbonate and a solution saturated with respect to that salt, and also practically saturated with respect to ammonium bicarbonate and ammonium nitrate at the temperature of the reaction; removing the precipitated sodium bicarbonate from the solution at the temperature of the reaction,'and washing it to remove adherent mother liquor; treating the.

solution from which the precipitated sodium bicarbonate has been removed in such a way as to remove practically all the remaining bicarbonate, and subsequently cooling it; separating from the cooled solution the ammonium nitrate which falls out; washing it with a substantially saturated solution of ammonium nitrate; and drying it.

2. The recess for the manufacture of commercialy pure ammonium nitrate, which consists in causin to react with formation 0t ammonium nitrate, such quantities ot sodium nitrate and ammonium bicarbonate in presence of such quantity of water as will yield, when the reaction is finished, a precipitate of sodium bicarbonate and a solution saturated with resphct to that salt,

to ammonium bicarbonate and ammonium nitrate at the temperature of the reaction;

removing the precipitated sodium bicarbonate from the solution at the temperature of the reaction, and washing it to remove adherent mother liquor; treating the solu-' with a substantially saturated solution of ammonium nitrate; and drying it. v

3. The improvement in the process of manufacturing commercially pure ammonium nitrate, which consists in causing to react with formation of ammonium nitrate,

vsuch quantities of sodium nitrate and a suitable reagent or reagents in the presence of such quantities of a solution containing ammonium nitrate and sodium nitrate as will yield, when the react-ion is finished, a'precipitate of sodium bicarbonate and a solution saturated with respect to that salt, and

also practically saturated with respect to ammonium bicarbonate and ammonium nitrate at the temperature of the reaction; removin the precipitated sodium bicarbonate from t e solution at the temperature of the reaction, and washing it to'remove adherent which the precipitated sodium bicarbonate has been removed in such a way as to remove practically all the remaining bicarbonate, and subsequently cooling it; separating from the cooled solution the ammonium nitrate which falls out; washing it with a substantially saturated solution of ammonium nitrate; and drying it.

4. The process for the manufacture of commercially pure ammonium nitrate, which consists in stirring together 200 parts of sodium nitrate, 210 parts of ammonium bi carbonate, and 100 parts of water, ata temperature of'about 22v 0., separating the precipitated sodium bicarbonate at the conclusion of the reaction at the same temperature, destroying the 'bicarbonates in the remaining solution and cooling it to -1 C., washing the precipitated ammonium nitrate with a substantially saturated solution of the same salt, and drying it.

In witness whereof, we have hereunto signed our names this 25 day of May 1911, in the presence of two subscribing witnesses.

F. a. FREETH. H. E. COGKSEDGE.

Witnesses:

H. WILLIAMS, H. O. DIXON.

mother liquor; treating the solution from 

